It is known from the literature (J. Mitola, “The Software Radio Architecture”, IEEE Communications Magazine, May 1995 and E. Buracchini, “The Software Radio Concept”, IEEE Communications Magazine, September 2000) that reconfigurable systems like terminals, base stations and network nodes, are equipments whose operative working mode may be reconfigured. For instance, a reconfigurable radio terminal able to work with a second generation system (2G), like GSM/GPRS (Global System for Mobile Communication/General Packet Radio Service), can be reconfigured in order to become able to work with a third generation system (3G), like UMTS (Universal Mobile Telecommunication System) or CDMA 2000 (Code Division Multiple Access 2000), with DVB-T (Digital Video Broadcasting Terrestrial) or with WLAN (Wireless Local Area Network) systems and so on. According to present disclosure, the term “system” is intended as a plurality of elements coordinated between them according to predetermined criteria, that is coordinated according to a “Standard”, in order to perform a specific function which is for instance that of operating as a communication network.
In the present document, examples of systems are the GSM system, the GPRS system, the UMTS system, the WLAN system and so on, each of them complying with a corresponding Standard.
In order to carry out the reconfiguration of a terminal, it is necessary—according to the above mentioned literature—that the operative functions of the terminal are realised with a technology which is reconfigurable. Concerning this, the reconfigurable terminals or devices are provided with a reprogrammable hardware constituted, for example, by a plurality of FPGAs (Field Programmable Gate Arrays), DSPs (Digital Signal Processors) and microprocessors: the single functionalities of the device, even at the lowest level, are performed by a software code. As a consequence, for reconfiguring a reprogrammable device, it suffices to replace the operating software managing the hardware of the device itself.
By the term “operating software” it is meant, in present description, the software, organised in libraries, which defines both the radio interface (e.g. L1, L2, L3) and the upper layers (e.g. L4 up to L7) of the protocol stack of a considered system, like for instance GSM/GPRS, UMTS and so on.
As known, in the telecommunication domain, the most employed method for obtaining a functional grouping is the OSI model (Open System Interconnection). The functionalities are grouped in functional planes represented under the form of a stack.
Each layer of the protocol stack provides services to the immediately higher layer, said services being in turn improvements of the services provided by the immediately lower layer.
The lowest layer (layer 1) is generally intended for physically transmitting the information.
According to the OSI specification, the standard number of layers is 7: respectively physical, connection, network, transport, session, presentation and application layer.
Each system, e.g. GSM/GPRS, UMTS and so on, implements the necessary part of the OSI protocol stack.
When considering a radio terminal, the benefits provided when using a reconfigurable hardware are many, but one benefit is evidently immediate: the radio terminal can be reconfigured according to the system covering the area where the terminal is located (working area). Therefore, if the terminal is used in an area covered by a second generation system, like GSM/GPRS, the terminal can be reconfigured in order to be able to receive said system; likewise, in an area covered by a third generation system, like UMTS, the terminal can be configured accordingly.
It is known from the literature (AA.VV. “Software Radio: The Challenges for Reconfigurable Terminals”, Annals of telecommunications—July/August 2002, GET Hermes and E. Buracchini “The Software Radio Concept”) that a software code may be transferred or downloaded to a terminal at least in three different ways:                via a smart card by using a SIM (Subscriber Identity Module) to be inserted inside the radio mobile terminal;        via an external connection by using for instance a link with a personal computer through an infrared/serial/USB (Universal Serial Bus) port;        via radio or over-the-air (OTA) by using a specific radio channel.        
Concerning software downloading, the fundamental steps of a generic protocol allowing to manage the downloading of a software to a terminal have been defined in the framework of the Software Defined Radio Forum (SDR Forum) as reachable via the URL www.sdrforum.org.
The protocol as defined by SDRF is of the client-server type, per se known.
The downloading protocol steps are the following ones:                download initiation: step during which the terminal communicates to the server, on which a software to be downloaded is resident, the intention to begin a software download;        mutual authentication; the terminal and the server must authenticate each other;        capability exchange: the server communicates the capability information relative to the software to be downloaded and the terminal verifies whether the software can be loaded into the terminal memory, installed therein and run;        download acceptance: the server communicates to the terminal the downloading, installation and billing options; the terminal decides whether the indications provided by the server are acceptable or not;        download and integrity test: during the software download, the received code must be tested; the terminal requests the retransmission of the incorrectly received radio blocks;        installation: during the installation step, the software billing and licensing conditions are provided by the server;        in-situ testing: before starting the software, the terminal carries out some tests with the help of test vectors downloaded together with the software code;        non repudiation exchange: once the software code has been installed and tested, the terminal confirms to the server that the installation was successful in order to start the billing procedure.        
It is known from prior art, e.g. E. Buracchini, “The Software Radio Concept”, IEEE Communications Magazine, September 2000, that the software downloading via radio or OTA foresees the use by the terminal of a radio channel. It is known—according to the above mentioned literature—to download the software code in two different ways, depending on the typology of the radio channel:                “out of band” way: by means of a “universal” channel independent from the current system, when the terminal is switched on, it automatically tunes to said channel and performs the download of the operating software relative to the system operating in the working area;        “in band” way: by using the radio channels of the standard cellular systems of second and third generation, like GSM/GPRS and UMTS respectively, this way provides that the terminal, already operating on one of these channels, can receives the operating software relative to a system different from that currently used; for instance, a reconfigurable terminal operating with a second generation system, like GSM/GPRS, can perform the download of a third generation system, like UMTS, by using the second generation radio channel according to which it is working.        
An example of “out of band” software download is for instance described in the Japanese Patent Application No. 2001061186. This document describes a system and a method for downloading software content over-the-air. When a radio terminal is switched on, it seeks on an universal channel what the current system in the working area is and carries out the software download relative to the indicated system.
Considering the “out of band” mode, according to prior art, it is needed to implement a dedicated radio channel and therefore dedicated equipments in the network for its implementation.
An example of “in band” software download is for instance described in the US Patent Application No. 2003/0163551. This document describes a system and a method for downloading software over-the-air by using dedicated channels during the negotiation steps between server and terminal (capability exchange, authentication, billing and so on), and by using shared common channels during the download procedure in order to provide the download service to as many users as possible simultaneously, without imposing a handicap on the available radio resources.
When considering the “in band” download way, the documents AA.VV., “Architecture Of IP Based Network Elements Supporting Reconfigurable Terminals”, SCOUT Workshop, 16 Sep. 2003, and IST-2001-34091 SCOUT, D4.1.1 “Requirements on network and security architecture and traffic management schemes for download traffic based on IP principles in cellular and ad hoc networks” suggest to modify deeply some protocols and some network nodes, e.g. the radio access nodes and/or Core Networks nodes based on release 5 and followings of UMTS, wherein the Core Network is completely based on IP (Internet Protocol), in order to make it possible to manage the download of the operating software.
Such modifications imply a considerable effort for the equipment manufacturers and for the network operators and dramatically impact on the Standards of the existing cellular systems.
Therefore the known “in band” techniques exhibit the limit that, when it is desired to add to an already existing cellular network, like for instance GSM/GPRS or UMTS, the operating software download management for reconfigurable terminals, heavy modifications to the protocols and to the network nodes are necessary.
Applicant notes that known prior art both in case of “in band” way and “out of band” way provides for deeply modifying some protocols and some network nodes.
A further problem of the known prior art is the management of the inter-system hand-over, that according to the present Standard, is defined as:                hand-over from a GSM/GPRS system to a UMTS system;        hand-over from a UMTS system to a CDMA 2000 system;        hand-over from a UMTS system to a GSM/GPRS system;        hand-over from a CDMA 2000 system to a UMTS system.        
According to the known standard the inter-system hand-over requires multimode terminals, i.e. terminals supporting the whole protocol stack of each cellular system by using ASIC (Application Specific Integrated Circuit) technology. See, for example, FIG. 1 showing a multimode terminal comprising a whole radio protocol stack of the GSM/GPRS system referenced as RAT GSM/GPRS, a whole radio protocol stack of the UMTS system referenced as RAT UMTS, and a whole radio protocol stack of the CDMA 2000 system referenced as RAT CDMA 2000.
The known solution has some disadvantages as high power consumption, big device size and high implementation costs.
In summary, Applicant notes that known prior art                does not solve the problem of downloading software without a huge modification of the network nodes, e.g. the addition of new nodes and interfaces, and to modify the data signalling and transferring protocols defined by the Standard, which could imply an inefficient use of the radio resources; and        is not able to use re-configurable terminals for managing inter system handover.        